Adapt website to use g3doc sources and bazel.

This adapts the merged website repository to use the image and bazel
build framework. It explicitly avoids the container_image rules provided
by bazel, opting instead to build with direct docker commands when
necessary.

The relevant build commands are incorporated into the top-level
Makefile.

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+# Performance Guide
+
+gVisor is designed to provide a secure, virtualized environment while preserving
+key benefits of containerization, such as small fixed overheads and a dynamic
+resource footprint. For containerized infrastructure, this can provide a
+turn-key solution for sandboxing untrusted workloads: there are no changes to
+the fundamental resource model.
+
+gVisor imposes runtime costs over native containers. These costs come in two
+forms: additional cycles and memory usage, which may manifest as increased
+latency, reduced throughput or density, or not at all. In general, these costs
+come from two different sources.
+
+First, the existence of the [Sentry](../) means that additional memory will be
+required, and application system calls must traverse additional layers of
+software. The design emphasizes [security](../security/) and therefore we chose
+to use a language for the Sentry that provides benefits in this domain but may
+not yet offer the raw performance of other choices. Costs imposed by these
+design choices are **structural costs**.
+
+Second, as gVisor is an independent implementation of the system call surface,
+many of the subsystems or specific calls are not as optimized as more mature
+implementations. A good example here is the network stack, which is continuing
+to evolve but does not support all the advanced recovery mechanisms offered by
+other stacks and is less CPU efficient. This is an **implementation cost** and
+is distinct from **structural costs**. Improvements here are ongoing and driven
+by the workloads that matter to gVisor users and contributors.
+
+This page provides a guide for understanding baseline performance, and calls out
+distint **structural costs** and **implementation costs**, highlighting where
+improvements are possible and not possible.
+
+While we include a variety of workloads here, it’s worth emphasizing that gVisor
+may not be an appropriate solution for every workload, for reasons other than
+performance. For example, a sandbox may provide minimal benefit for a trusted
+database, since _user data would already be inside the sandbox_ and there is no
+need for an attacker to break out in the first place.
+
+## Methodology
+
+All data below was generated using the [benchmark tools][benchmark-tools]
+repository, and the machines under test are uniform [Google Compute Engine][gce]
+Virtual Machines (VMs) with the following specifications:
+
+    Machine type: n1-standard-4 (broadwell)
+    Image: Debian GNU/Linux 9 (stretch) 4.19.0-0
+    BootDisk: 2048GB SSD persistent disk
+
+Through this document, `runsc` is used to indicate the runtime provided by
+gVisor. When relevant, we use the name `runsc-platform` to describe a specific
+[platform choice](../platforms/).
+
+**Except where specified, all tests below are conducted with the `ptrace`
+platform. The `ptrace` platform works everywhere and does not require hardware
+virtualization or kernel modifications but suffers from the highest structural
+costs by far. This platform is used to provide a clear understanding of the
+performance model, but in no way represents an ideal scenario. In the future,
+this guide will be extended to bare metal environments and include additional
+platforms.**
+
+## Memory access
+
+gVisor does not introduce any additional costs with respect to raw memory
+accesses. Page faults and other Operating System (OS) mechanisms are translated
+through the Sentry, but once mappings are installed and available to the
+application, there is no additional overhead.
+
+{% include graph.html id="sysbench-memory" url="/performance/sysbench-memory.csv" title="perf.py sysbench.memory --runtime=runc --runtime=runsc" %}
+
+The above figure demonstrates the memory transfer rate as measured by
+`sysbench`.
+
+## Memory usage
+
+The Sentry provides an additional layer of indirection, and it requires memory
+in order to store state associated with the application. This memory generally
+consists of a fixed component, plus an amount that varies with the usage of
+operating system resources (e.g. how many sockets or files are opened).
+
+For many use cases, fixed memory overheads are a primary concern. This may be
+because sandboxed containers handle a low volume of requests, and it is
+therefore important to achieve high densities for efficiency.
+
+{% include graph.html id="density" url="/performance/density.csv" title="perf.py density --runtime=runc --runtime=runsc" log="true" y_min="100000" %}
+
+The above figure demonstrates these costs based on three sample applications.
+This test is the result of running many instances of a container (50, or 5 in
+the case of redis) and calculating available memory on the host before and
+afterwards, and dividing the difference by the number of containers. This
+technique is used for measuring memory usage over the `usage_in_bytes` value of
+the container cgroup because we found that some container runtimes, other than
+`runc` and `runsc`, do not use an individual container cgroup.
+
+The first application is an instance of `sleep`: a trivial application that does
+nothing. The second application is a synthetic `node` application which imports
+a number of modules and listens for requests. The third application is a similar
+synthetic `ruby` application which does the same. Finally, we include an
+instance of `redis` storing approximately 1GB of data. In all cases, the sandbox
+itself is responsible for a small, mostly fixed amount of memory overhead.
+
+## CPU performance
+
+gVisor does not perform emulation or otherwise interfere with the raw execution
+of CPU instructions by the application. Therefore, there is no runtime cost
+imposed for CPU operations.
+
+{% include graph.html id="sysbench-cpu" url="/performance/sysbench-cpu.csv" title="perf.py sysbench.cpu --runtime=runc --runtime=runsc" %}
+
+The above figure demonstrates the `sysbench` measurement of CPU events per
+second. Events per second is based on a CPU-bound loop that calculates all prime
+numbers in a specified range. We note that `runsc` does not impose a performance
+penalty, as the code is executing natively in both cases.
+
+This has important consequences for classes of workloads that are often
+CPU-bound, such as data processing or machine learning. In these cases, `runsc`
+will similarly impose minimal runtime overhead.
+
+{% include graph.html id="tensorflow" url="/performance/tensorflow.csv" title="perf.py tensorflow --runtime=runc --runtime=runsc" %}
+
+For example, the above figure shows a sample TensorFlow workload, the
+[convolutional neural network example][cnn]. The time indicated includes the
+full start-up and run time for the workload, which trains a model.
+
+## System calls
+
+Some **structural costs** of gVisor are heavily influenced by the [platform
+choice](../platforms/), which implements system call interception. Today, gVisor
+supports a variety of platforms. These platforms present distinct performance,
+compatibility and security trade-offs. For example, the KVM platform has low
+overhead system call interception but runs poorly with nested virtualization.
+
+{% include graph.html id="syscall" url="/performance/syscall.csv" title="perf.py syscall --runtime=runc --runtime=runsc-ptrace --runtime=runsc-kvm" y_min="100" log="true" %}
+
+The above figure demonstrates the time required for a raw system call on various
+platforms. The test is implemented by a custom binary which performs a large
+number of system calls and calculates the average time required.
+
+This cost will principally impact applications that are system call bound, which
+tend to be high-performance data stores and static network services. In general,
+the impact of system call interception will be lower the more work an
+application does.
+
+{% include graph.html id="redis" url="/performance/redis.csv" title="perf.py redis --runtime=runc --runtime=runsc" %}
+
+For example, `redis` is an application that performs relatively little work in
+userspace: in general it reads from a connected socket, reads or modifies some
+data, and writes a result back to the socket. The above figure shows the results
+of running [comprehensive set of benchmarks][redis-benchmark]. We can see that
+small operations impose a large overhead, while larger operations, such as
+`LRANGE`, where more work is done in the application, have a smaller relative
+overhead.
+
+Some of these costs above are **structural costs**, and `redis` is likely to
+remain a challenging performance scenario. However, optimizing the
+[platform](../platforms/) will also have a dramatic impact.
+
+## Start-up time
+
+For many use cases, the ability to spin-up containers quickly and efficiently is
+important. A sandbox may be short-lived and perform minimal user work (e.g. a
+function invocation).
+
+{% include graph.html id="startup" url="/performance/startup.csv" title="perf.py startup --runtime=runc --runtime=runsc" %}
+
+The above figure indicates how total time required to start a container through
+[Docker][docker]. This benchmark uses three different applications. First, an
+alpine Linux-container that executes `true`. Second, a `node` application that
+loads a number of modules and binds an HTTP server. The time is measured by a
+successful request to the bound port. Finally, a `ruby` application that
+similarly loads a number of modules and binds an HTTP server.
+
+> Note: most of the time overhead above is associated Docker itself. This is
+> evident with the empty `runc` benchmark. To avoid these costs with `runsc`,
+> you may also consider using `runsc do` mode or invoking the [OCI
+> runtime](../../user_guide/quick_start/oci/) directly.
+
+## Network
+
+Networking is mostly bound by **implementation costs**, and gVisor's network stack
+is improving quickly.
+
+While typically not an important metric in practice for common sandbox use
+cases, nevertheless `iperf` is a common microbenchmark used to measure raw
+throughput.
+
+{% include graph.html id="iperf" url="/performance/iperf.csv" title="perf.py iperf --runtime=runc --runtime=runsc" %}
+
+The above figure shows the result of an `iperf` test between two instances. For
+the upload case, the specified runtime is used for the `iperf` client, and in
+the download case, the specified runtime is the server. A native runtime is
+always used for the other endpoint in the test.
+
+{% include graph.html id="applications" metric="requests_per_second" url="/performance/applications.csv" title="perf.py http.(node|ruby) --connections=25 --runtime=runc --runtime=runsc" %}
+
+The above figure shows the result of simple `node` and `ruby` web services that
+render a template upon receiving a request. Because these synthetic benchmarks
+do minimal work per request, must like the `redis` case, they suffer from high
+overheads. In practice, the more work an application does the smaller the impact
+of **structural costs** become.
+
+## File system
+
+Some aspects of file system performance are also reflective of **implementation
+costs**, and an area where gVisor's implementation is improving quickly.
+
+In terms of raw disk I/O, gVisor does not introduce significant fundamental
+overhead. For general file operations, gVisor introduces a small fixed overhead
+for data that transitions across the sandbox boundary. This manifests as
+**structural costs** in some cases, since these operations must be routed
+through the [Gofer](../) as a result of our [security model](../security/), but
+in most cases are dominated by **implementation costs**, due to an internal
+[Virtual File System][vfs] (VFS) implementation that needs improvement.
+
+{% include graph.html id="fio-bw" url="/performance/fio.csv" title="perf.py fio --engine=sync --runtime=runc --runtime=runsc" log="true" %}
+
+The above figures demonstrate the results of `fio` for reads and writes to and
+from the disk. In this case, the disk quickly becomes the bottleneck and
+dominates other costs.
+
+{% include graph.html id="fio-tmpfs-bw" url="/performance/fio-tmpfs.csv" title="perf.py fio --engine=sync --runtime=runc --tmpfs=True --runtime=runsc" log="true" %}
+
+The above figure shows the raw I/O performance of using a `tmpfs` mount which is
+sandbox-internal in the case of `runsc`. Generally these operations are
+similarly bound to the cost of copying around data in-memory, and we don't see
+the cost of VFS operations.
+
+{% include graph.html id="httpd100k" metric="transfer_rate" url="/performance/httpd100k.csv" title="perf.py http.httpd --connections=1 --connections=5 --connections=10 --connections=25 --runtime=runc --runtime=runsc" %}
+
+The high costs of VFS operations can manifest in benchmarks that execute many
+such operations in the hot path for serving requests, for example. The above
+figure shows the result of using gVisor to serve small pieces of static content
+with predictably poor results. This workload represents `apache` serving a
+single file sized 100k from the container image to a client running
+[ApacheBench][ab] with varying levels of concurrency. The high overhead comes
+principally from the VFS implementation that needs improvement, with several
+internal serialization points (since all requests are reading the same file).
+Note that some of some of network stack performance issues also impact this
+benchmark.
+
+{% include graph.html id="ffmpeg" url="/performance/ffmpeg.csv" title="perf.py media.ffmpeg --runtime=runc --runtime=runsc" %}
+
+For benchmarks that are bound by raw disk I/O and a mix of compute, file system
+operations are less of an issue. The above figure shows the total time required
+for an `ffmpeg` container to start, load and transcode a 27MB input video.
+
+[ab]: https://en.wikipedia.org/wiki/ApacheBench
+[benchmark-tools]: https://github.com/google/gvisor/tree/master/benchmarks
+[gce]: https://cloud.google.com/compute/
+[cnn]: https://github.com/aymericdamien/TensorFlow-Examples/blob/master/examples/3_NeuralNetworks/convolutional_network.py
+[docker]: https://docker.io
+[redis-benchmark]: https://redis.io/topics/benchmarks
+[vfs]: https://en.wikipedia.org/wiki/Virtual_file_system